In the prior art, so-called active type three-dimensional measurement apparatuses have been known that capture three-dimensional data by projecting a reference beam on a target object and receiving its reflected light. Among these types of devices, an apparatus that can generate both a range image (the image used to measure distance and to calculate the three-dimensional shape of the target object) and a color image (the image used to display the target object) is known, as disclosed for example, in Japanese Patent Unexamined Publication No. 9-145319.
FIG. 19 is a block diagram showing the configuration of such an active type three-dimensional measurement apparatus. Referring to the figure, a beam splitter (beam-splitting prism) 52 is constructed with a color separation film (dichroic mirror) 521, two prisms 522 and 523 sandwiching the color separation film 521, a range image capturing CCD sensor 53 provided on the emergent face of the prism 522, and a color image capturing CCD sensor 54 provided on the emergent surface of the prism 523.
A target object is scanned by a reference beam emitted from a semiconductor laser, and the light reflected by the target object enters a light receiving lens 51a. The light that enters the light receiving lens 5 la passes through the prism 522 and reaches the color separation film 521. Light U0 lying in the oscillation wavelength region of the semiconductor laser is reflected by the color separation film 521 and directed toward the range image capturing CCD sensor 53. On the other hand, light C0 transmitted through the color separation film 521 passes through the prism 523 and enters the color image capturing CCD sensor 54.
The range image capturing CCD sensor 53 is driven by a range image capturing CCD driver 204. The color image capturing CCD sensor 54 is driven by a color image capturing CCD driver 203. The output of the range image capturing CCD sensor 53 is processed by an A/D converter (an output processing circuit) 202, and then stored in a range image frame memory 206. The output of the color image capturing CCD sensor 54 is processed by an A/D converter (an output processing circuit) 201, and then stored in a color image frame memory 205.
The prior art active type three-dimensional measurement apparatus described above has exhibited the following limitations, due to the use of the two CCD sensors 53 and 54.
(1) The mounting positions of the two CCD sensors must be adjusted very precisely so as to eliminate misregistration between the range image and the color image.
(2) Since near infrared light is primarily used for the reference beam, it is necessary to produce a prism that can separate incident light into near infrared light for the range image and visible light for the color image.
(3) The quality of the color image is dependent on the spectral characteristics of the prism that is used.
The present invention has been devised to address the above-listed limitations, and one object of the invention is to solve the problems associated with the use of two sensors in a three-dimensional measurement apparatus.